Means for boiling fibrous matters



June 28 1927. 1,634,143

N. K. F. HANSON I MEANS FOR BOILING FIBROUS MATTERS Filed March 11. 1926 80 as a result ofthe digesting process is re:

Patented June 28, .1927.

UNITED STATES PATENT OFFICE.

NILS KNU'I. FREDRIK HANSON, OF S TOCKHOLM, ,SWEDEN.

MEANS FOR BOILINGFIZBROUS MATTERS.

Application filed March 11, 1926, Serial No. 93,986, and in Sweden October 18, 1924.

ing the pulp with an acid salt, as bisulphite,

comprising sulphurous acid dissolved in water, said acid solution containing in turn a solution of monosulphite (as calcium sulphite, magnesium sulphite or the like). In suchdigesting process the free sulphurous acid active in the process of extracting the incrusting substanceswill be caused to withdraw from the digesting liquid to an extent depending on the temperature and-the pres-/ sure inside the digester. The. sulphurous acid thus released collects above the wood and liquid contained in the digester and does not, consequently, assist to the extraction of the incrustin substances.

The invention has for its object to causesaid sulphurous acid to assist to the extraction of the incrusting substances whereby a considerable reducin of the duration of the digesting process is obtained.

lVith this ObJcCt in view the gas produced moved from the upper portion of the digester and again introduced into the digester at the bottom thereof so as to be caused to pass upwardly through the digester. The gas is in this way caused to pass the whole height of wood and liquid contained within the digester and will during said passage engage theincrusting substances to assist to the extraction thereof from the wood.

By said circulation of the gas two further advantages are obtained, that is, on the one hand, an improved distribution of the temperature inside the digester and, on the other hand, an improved circulation of the liquid,-which advantages result in a more uniform output.

It has already been proposed to improve thedistribution of the temperature and the circulation of the li uid by circulation of the liquid itself, such circulation however, will be ineflicient as compared with our improved circulation of the gas and does not, moreover, render the free gas available for the extracting process.

In the accompanying drawing a plant embodying .the principles of this invention is shown diagrammatically.

Referring to the drawing, the numeral 1 represents any desired type-of sulphite pulp digester. Extending from the'top of the digester are two pipes 2 and 3 each connected atits other end to the top of a receptacle 4 and 5, respectively. Inserted in each of'said as a result of an increase of the pressure inside the respective receptacle and close due to a suction from the receptacle.

Extending from the lower portion of each receptacle 4 and 5 is a. pipe 12 and 13, respectively, each of which divides into two branches connected to the inlet and outlet, respectively, of a centrifugal .pumpor the like 14. Each of the four pipe branches thus formed is provided with a valve 15, 16, 17, 18, respectively. Said valves are adapted to be controlled in such a way that one of the two valves associated with one and the same pair of branches is open and the other closed when the corresponding valves of the other pair of branches is, respectively, closed and open, thus enabling the. pump to efifect a transmission of liquid in either direction between the two receptacles.

The control of the valves is, preferably, effected automatically by means controlled by the liquid levels within the receptacles, asin dicatedat 19 and 20 in the drawing.

The operation of theplantJis as follows:

Let it be assumed that one of the recepta-.

. 4 to the-receptacle 5. As a result, gas is drawn out from" the upper portion of the digester 1 through the pipe 2, while gas that may be contained in thereceptacle 5 as a result of a .precedin suction operation similar to that above escribed, will be caused to enter the lower portion of the digester through pipe 9 and pass upwardly through the digester while assisting to the extraction of the incrusting substances, as already men tioned. The receptacle 4- havin been emptied of liquid and the receptac e 5 having been filled with this liquid the valves '-18 are reversed so as to cause the liquid to be returned from receptacle 5 to receptacle 4. As this return movement of the liquid proceeds gas is drawn into the receptacle 5 from the upper portion 'of the digester, while the gas previously drawn into the receptacle 4 is caused to enter the digester at the bottom thereof through pipe 8.

By alternate'filling and emptying the receptacles 4 and 5 in the way described a practically continuous gas transfer may be-efi fected outside the digester from the upper to the lower portion thereof.

If the reversing of the valves 15- 18 be effected when either of the receptacles 4 or 5 is completely filled with liquid any clearance is avoided and the gas current will be as continuous as possible.

It is to be noted that variations may be made Without departing from the principle of the invention. Thus, for instance, a single receptacle may be used for effecting the circulation of the gas. In such case, said reneptacle is caused to alternately act by suction and pressure, while another receptacle is provided merely for the purpose of receiving the liquid. If desired, the liquid may be eas es substituted by steam or gas under pressure in which case steam or gas valves are substituted for the valves 1518.

said connection, separate connections between each receptacle and the top and bottom of said digester, and back-pressure valves inserted in said last-mentioned connections.

2. An apparatus for treating fibrous matters in order. to exact viscous substances therefrom comprising a digester, two receptacles adapted to be alternately filled with liquid; a connection between said receptacles, a liquid pump mechanism in said connection, means controlled by the liquid lever in said receptacles to reverse the flow of liquid in, said connection, separate connections between each of said receptacles and the top and bottom of the digester, and back-pressure valves in said last-mentioned connections.

- In testimony whereof I have signed my name.

NILS KNUT FREDRIK HANSON. 

